Due to morbidity and limited amounts of material, alternatives to autologous grafts for bone repair are desirable. Mixtures of marrow stromal cells (MSC) and carrier matrices are known to augment bone repair. Increasing the number of MSC through ex vivo expansion may significantly increase the amount and rate of new bone formation. In this proposal, the ability of an automated clinical-scale cell culture system, the AastromReplicell (tm) Cell Production System (AR/CPS), to generate large numbers of MSC with osteogenic potential will be tested. Osteoprogenitor cells will be identified by flow cytometry (STRO-1 +, CD63+), ability to form mineralized matrix in vitro, and ability to form bone in SCID/NOD mice. Using small-scale cultures, parameters including medium perfusion rates, culture duration, and the effects of additives such as dexamethasone, ascorbate, FGF-2 and BMP-2, will be studied. Conditions found optimal for osteoprogenitor cell production will then be tested in the AR/CPS to confirm feasibility at the clinical scale. With successful completion of these studies, MSC generated in the AR/CPS will be tested in clinical trials to establish the safety and efficacy of these cells in treating nonunion fractures. In addition, this work may lead to novel treatments for skeletal diseases such as osteoporosis and osteoarthritis.